The soldier was on duty in the Nahr-e Saraj district of Helmand province on Friday 17 August when he was killed by enemy action.
Spokesman for Task Force Helmand, Major Ian Lawrence, said:
It is with great sadness I must inform you that a soldier from the 1st Battalion Grenadier Guards has been killed whilst on sentry duty in the Nahr-e Saraj district of Helmand province.
The thoughts and prayers of everyone in the Task Force are with his family and friends at this very difficult time.
The soldier’s family have been informed and have asked for a period of grace before further details are released.